Certain known bar code readers rely upon optical sensors which are located a fixed focal length away from the bar code being detected. This may be accomplished by operating a bar code transducer in contact with the surface upon which the bar code is printed. In other bar-code readers, collimated light from a laser is used to scan a bar code on or near a plane of detection. In these and other conventional bar-code readers the object bearing the bar code being detected is usually referenced at a fixed focal distance from the detector in order to pick up a sharp, optical reproduction of an image of the bar code. Also, known bar-code readers commonly require normalizing schemes to assure proper sensing of bar codes that are printed on materials of different background colors and textures, and that are to be detected under varying ambient lighting conditions. Further, known bar-code readers terminate operations for a brief period if insufficient reflected light is received, and then periodically test for sufficient reflected light indicative of close proximity of the reader to a reflective surface. Readers of this type are disclosed in the literature (see, for example, U.S. Pat. No. 3,925,639).